The present application relates generally to the caching of data communications over computer networks such as, e.g., the Internet, a local area network, a wide area network, a wireless network, and others.
Caching of data communications over computer networks is a well-known network optimization technique, affording improvement of application performance and optimal utilization of network resources through storing and delivering popular content close to end users.
Content caching solutions have traditionally focused on caching of client-server communications, e.g., Web browsing or streaming sessions, where the cache intermediates delivery of content objects (e.g., text files and images in case of Web browsing) from server to client.
The content applications supported by the caching solutions are designed to support caching; they do not utilize end-to-end encryption of the data session, and they have optional client-side explicit support for caching and utilize well-known data ports (tcp/80 for HTTP, tcp/1935 for RTMP, etc.).
The data sessions established by Web browsing and streaming applications are atomic. Each such session incorporates all information needed for the cache to identify a content query, content object (or portion of it) requested, and address of the content source where the object may be maintained.
The traditional caching solutions accordingly implement the following caching methodology:                (a1) receiving the data session from the client or (a2) identifying and intercepting the data session between the client and content source, using well-known TCP or UDP port or ports or through Layer7 analysis of the data protocol, using a redirecting network element or otherwise;        (b) parsing the data protocol used by the client to identify a data query within the session;        (c) identifying a unique data object (or portion of it) requested by the client; and        (d1) matching the data query with a data response stored in cache and sending the response to the client or (d2) propagating the data query to the server (content source), receiving the response from the server, optionally storing the response in the cache, and sending the response to the requesting client.        
In recent years, Internet applications have evolved in functionality and complexity, using dynamic content object identifiers (e.g., HTTP URLs) that survive in the scope of one download session only, supporting transfer of the same content object over several concurrent sessions, from multiple content sources, involving multiple dynamic ports, involving end-to-end encryption of the data sessions. These new applications include multiple types of peer-to-peer (P2P) applications for file sharing and streaming, adaptive bitrate protocols for delivery of video over HTTP, HTTP download accelerators, and software update services such as Microsoft Windows Update.
The peer-to-peer applications typically implement a mechanism of “peer discovery” where the client application accesses the P2P network, queries the network to discover content sources that may offer the content object, and subsequently establishes data sessions with these content sources, with some of these sessions using end-to-end encryption.
It is a common practice for content sources in P2P networks to use dynamic rather than static “well-known” ports.
P2P applications can employ encryption of the session in such a way as to avoid detection by network elements, using Layer7 criteria for session identification.
As a result, traditional caching solutions cannot identify and intercept these data sessions, nor are they able to parse the data protocol to identify the data query, due to the encryption.
Non-P2P applications (e.g., download accelerators, adaptive bitrate video clients, software update services, and others) commonly establish multiple sessions to arrange retrieval of the same content object, where each separate session does not offer all the information needed for the cache to identify the requested data object and/or match a data request with a data response.
The features exhibited by these new applications obviate traditional caching methodology. It would be desirable to provide alternative approaches to content caching to support such new applications.